1. Field of the Invention
The present invention relates to a cooling fan that can be favorably used in a flat panel display apparatus such as a thin-screen television and to an image display apparatus. In more detail, the present invention relates to a cooling fan for cooling a backlight unit that is a high-temperature region in a flat panel display apparatus, the cooling fan being especially capable of uniformly cooling the backlight unit of a large flat panel display apparatus with high efficiency and operating more quietly than conventional fans.
2. Description of the Related Art
Fans are conventionally used in a flat panel display apparatus such as a thin-screen television to cool the backlight that is both a light source for the display panel and also a high-temperature region. Propeller fans are superior for such use due to their high efficiency and quiet operation.
A display apparatus equipped with a propeller fan as the cooling fan for cooling a plasma display panel, for example, has been disclosed (see, for example, Patent Document 1).
In Patent Document 1, a plurality of ventilation holes and a cooling fan are provided at either end of a gap for allowing air to flow over a plasma display panel, at positions corresponding to gaps in a housing. Warm air that has been heated within the gap next to the plasma display panel is efficiently expelled from the housing by the cooling fan, thereby preventing the temperature inside the plasma display panel from rising.
Patent Document 1
Japanese Laid-Open Patent Publication No. H09-275534
However, there are the following problems for a television such as the plasma display panel mentioned above. Factors such as the apparatus design and installation conditions for the fan make it difficult to provide sufficient circular area for a propeller fan. In addition, although a reduction in the fan tip speed is desired in order to satisfy demands for extremely quiet operation, a larger circular area becomes necessary to achieve the required air flow, and therefore there arises a problem that the demand for quiet operation cannot be satisfied.
Aside from the propeller fans mentioned above, cross flow fans, sirocco fans and the like are also used. Since such fans generate airflows in all directions of the rotating surfaces, there are the problems of poor efficiency for use as cooling fans and a high noise level.